<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>理解 HTML 元素的特性</title>
</head>
<body>
<span>abc <span>xyz</span> def</span>

<hr>

<span>abc <div>xyz</div> def</span>

<hr>

<span style="width: 200px; height: 2000px; background-color: red">abc</span>

<h1>Hello, <h2>Hi</h2>World!</h1>
<hr>
<div>abc
    <h3>uvw
        <div>xyz
            <hr>


</body>
</html>